This invention relates to scanning display devices and optical eyepieces, and more particularly to a retinal scanning display having a multi-functional eyepiece.
A virtual retinal display device is an optical device for generating an image upon the retina of an eye. Light is emitted from a light source, passed through a lens, then deflected along a scan path by a scanning device. At a distance defined by the lens the scanned light converges to a focal point for each pixel position. As the scanning occurs the focal point moves along to define an intermediate image plane. The light then diverges beyond the plane. An eyepiece is positioned along the light path beyond the intermediate image plane at some desired focal length. An "exit pupil" occurs shortly beyond the eyepiece in an area where a viewer's eye pupil is to be positioned.
A viewer looks into the eyepiece to view an image. The eyepiece receives light that is being deflected along the scan path. Light thus impinges on the viewer's eye pupil at differing angles at different times during the scanning cycle. This range of angles determines the size of the image perceived by the viewer. Modulation of the light during the scanning cycle determines the content of the image. For a see-through virtual retinal display a user sees the real world environment around the user, plus the added image of the display projected onto the retina.